JMU AFV Lab Blog

I saw this article in ScienceDaily and was fascinated by it. (For more on this idea, go to this article at greencarcongress.com.) It seems like such an “elegant” idea to generate electricity for a hybrid vehicle. Being the questioning person I am, I immediately wondered why they would use permanent magnets instead of an electromagnet in the core of the “alternator.” After all the alternator in modern motor vehicles uses a small wire wound electromagnet as the “rotor” and a relatively larger coil as the “stator” to produce electricity to recharge the battery and provide power for electricity needs of the vehicle. These alternators use slip rings with carbon “brushes” to transmit voltage to the rotor to energize it. In this “Linear Alternator,” instead of rings, linear strips of metal on the connecting rod with brushes attached to the case could energize the coil.  Of course proper orientation of the moving coils and their magnetic lines of flux relative to the orientation of the stationary, current producing, coils would have to be taken into consideration.  My opinion is that the engine would have to be “fatter” in the alternator section to be more effective as an alternator.  What do you think?  (I can see this as a future project for the AFV Lab.)

free-piston-linear-alternator

ScienceDaily (Sep. 17, 2008) — In an advance toward introduction of an amazing new kind of internal combustion engine, researchers in China are reporting development and use of a new and more accurate computer model to assess performance of the so-called free-piston linear alternator (FPLA).

Their study of the FPLA, which could provide a low-emission, fuel efficient engine for future hybrid electric vehicles, is scheduled for the Sept. 17 issue of ACS’ Energy & Fuels, a bi-monthly journal.

Qingfeng Li and colleagues point out that the FPLA has only one moving part and is an engine designed to generate electricity. In the device, a piston in a cylinder shuttles between two combustion chambers. Permanent magnets on the piston generate electricity by passing through the coils of an alternator centered on the cylinder. The engine can burn a variety of fuels, including natural gas and hydrogen, and seems ideal use in a future world of climate change and possible fossil fuel shortages, they suggest.

Their report describes development of a better computer model to evaluate performance of the FPLA and guide engineers in construction of the engine. Results of their initial simulations showed that the FPLA could accelerate three times faster than other internal combustion engines and burns fuel in ways that minimize air pollution. “It is an environmentally friendly power source for the future,” the report concludes.

Journal reference:

1. Li, Qingfeng, Xiao, Jin, and Huang, Zhen. Simulation of a Two-Stroke Free-Piston Engine for Electrical Power Generation. Energy Fuels, 2008; DOI: 10.1021/ef800217k

Also see: http://www.greencarcongress.com/2008/09/modeling-a-free.html